The project represents a continued study of the biochemical cytology of Trichomonas vaginalis, a sexually transmitted common parasite that causes vaginitis and urethritis in humans. This organism is characterized by fermentative metabolism with hydrogen as a major endproduct and thee presence of hydrogenosomes, characteristic organelles of pyruvate metabolism. These organelles replace mitochondria and can be regarded as their anaerobic equivalents. Their enzyme composition resembles in many respects that of primitive anaerobic bacteria. The project aims at further exploration of the hydrogenosomes of T. vaginalis with the aim of obtaining information on the biological nature and phyletic relationships of this organelle. The primary structure of several hydrogenosomal proteins will be determined by molecular cloning starting from mRNA and compared with that of homologous molecules from prokaryotic and eukaryotic microorganisms and organelles for which amino acid sequence data are available. The existence of extension(s) and sequences within the mature protein that could play a role in intracellular targeting of these proteins will also be explored. To establish the relationships with other membrane bounded organelles the biosynthesis of hydrogenosomal proteins and the incorporation of newly synthesized polypeptides into isolated organelles will be studied. Regulation of these processes will be studied with the use of organisms with deficient hydrogenosomes.